1. Field of the Invention
This invention relates to improvements in a mechanism for locking both the opened and closed states of a foldable baby carriage.
2. Description of the Prior Art
An example of a foldable baby carriage to which this invention is applicable is disclosed in Japanese Patent Application No. 132136/1979 (Japanese Patent Application Laid-Open No. 57574/1981, Japanese Patent Publication No. 50705/1982; substantially corresponding to U.S. Pat. No. 4,317,581). The baby carriage disclosed therein comprises, as parts which enable the folding thereof, a pair of rear legs extending rearwardly downward from the middle of the baby carriage, a pair of support angle members turnably connected respectively to the middle portions of said rear legs so that they are turnable to extend along the upper or lower halves of the rear legs, a pair of push rods turnably connected at their lower ends to the middle portions of the support angle members, a pair of sleeves axially slidably installed adjacent the lower ends of the push rods, and springs for urging the sleeves to slide downward. Further, each support angle member is formed at its end (the other end) opposite to one end thereof connected to the rear leg with an engaging portion engageable by the sleeve for locking the opened state.
In such baby carriage, when it is opened, the support angle members are positioned along the upper halves of the rear legs while the other ends of the support angle members are aligned with the push rods, whereupon the sleeves slide downward until they engage the open state locking-purpose engaging portions of the support angle members. Thereby, the aligned state of the push rods and support angle members is maintained, with the result that the opened state of the baby carriage is locked.
Further, Japanese Patent Application No. 84159/1980 (Japanese Patent Application Laid-Open No. 11168/1982, Japanese Patent Publication No. 32065/1983) discloses a baby carriage of the same basic construction as in said first application, with the following improvements applied thereto. In the baby carriage of this second application, to lock both the opened and closed states, the support angle member is additionally formed with a closed state locking-purpose engaging portion, while the sleeve is designed to be engageable with both the opened and closed state locking-purpose engaging portions of the sleeve. In the opened state of the baby carriage, the situation is the same as in the first application described above, but in the closed state of the baby carriage, each support angle member is positioned along the lower half of the rear leg while the middle portion of the support angle member intersects the push rod, and in this state, each sleeve engages the closed state locking-purpose engaging portion of the support angle member, thereby locking this closed state.
According to this second application, both the opened and closed states of the baby carriage are locked by using such common members as the sleeves, so that a reduction in the number of parts can be expected.
However, in said second application, when the simplicity of operation is further investigated, it is seen that there is still room for improvement. That is, when it is desired to change the opened or closed state of the baby carriage to its closed or opened state, respectively, it is necessary to first remove the locking. This removal of the locking is attained by sliding the sleeve along the push rod to escape from the opened or closed state locking-purpose engaging portion, but since the sleeve is urged by a spring to move in a direction for engagement with the opened or closed state locking-purpose engaging portion, it is necessary that the force required to cause the sleeve to escape from said engaging portion be applied continuously at least in the early period of operation for opening or closing the baby carriage. On the other hand, in the case of means being provided for maintaining the sleeve in its state escaping from the engaging portion against the force of the spring, it is necessary that at the end of the opening or closing operation, said means for maintaining said state of escape be operated again to allow the sleeve to engage the engaging portion.
As for a technique for eliminating said inconvenience in operation, there is one disclosed in Japanese Patent Application No. 66274/1981 (Japanese Patent Application Laid-Open No. 182566/1982). In this third application, which is an improvement on said second application, the arrangement for maintaining the state of the sleeve escaping from the engaging portion is adopted on the one hand and on the other hand means is provided for canceling the escape state of the sleeve in the course of operation from the opened to the closed state of the baby carriage and in the course of operation from the closed to the opened state thereof, so that finally, when the baby carriage is brought to its opened or closed state, the sleeve automatically engages the opened or closed state locking-purpose engaging portion.
In this third application, there is provided a lock start member arranged like a cam adapted to rotate together with a foldable push rod connecting member for connecting a pair of push rods, said lock start member being adapted to act on an operating lever which controls the sleeve movement to prepare for locking the opened or closed state of the baby carriage. The lock start member is adapted to turn in response to the folding movement of the push rod connecting member, and the folding movement of the push rod connecting member is attained because the distance between the pair of push rods changes depending on whether the baby carriage is in its opened or closed state.